My invention is a mechanical system providing protection for unrestricted use of extremely sensitive and delicate piezoelectric chip pressure sensors in hostile industry environments. The art of building an extremely accurate piezoelectric sensor on a miniature silicon chip has developed to the extent that very inexpensive sensors are readily available. However, their nature is such that several parameters must be very closely controlled to keep variables other than the target change of pressure from grossly distorting their output, or from completely destroying the chip.
The following is a list of parameters my invention addresses and controls to make it practical and economical to use these inexpensive sensors in critical hostile environments:
1. It is highly possible that the instrument will experience pressures far above the design range of the sensor chip. A means must be provided to protect the sensor from medium pressures 10 to 100 times greater than what the sensor itself can withstand. Very severe pressure surges, pulses and oscillation can occur from water hammer and/or "noise" caused by pumps, throttling valves, etc. The sensor chip must be isolated from these destructive forces.
2. It is possible that the temperature of the environment surrounding the instrument can vary considerably (e.g., -50.degree. F. to +200.degree. F.). Therefore, the mechanical design of the sensor/transmitter system must be such that temperature change has minimum effect on the output signal.
3. Because the sensor is basically a subminiature strain gage, the system must eliminate the possibility of strain within the system being transferred to the sensor and being interpreted as a pressure induced output change.
4. Vibration is a common variable found in industry. The sensor and all related mechanical interface parts must be designed to withstand vibration over a long period of time. The design must also minimize the inertia and movement energy that can be conveyed to the sensor as a pressure pulse, thus resulting in a noisy signal in the presence of vibration.